I know there are scales that automatically upload your weight (I think withings sell them?).
I think not weaseling is pretty core to beeminder, and if you lose that you’ve lost the usefulness of it? If you’re struggling with this particular goal and not others, you risk building a habit of weaseling. So, maybe you should drop this goal for now, until you build up your habit / commitment to that meta-goal of not weaseling?
Finally, here are some weight-loss/maintenance tricks that helped me (and still do) without needing to count calories Article about this new trend of weight-loss wagering and what a scam it is (context for that).